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The proximity of the Ali Ou Daoud Zn-Pb ore deposit (AOD) to the Ikkou Ou Ali diapiric and magmatic paleohigh raises the question of the role of halokinesis and magmatism in the emplacement of the ore. The AOD ore deposit is hosted in hydrothermally dolomitized Bajocian carbonates. The mineralogical paragenetic sequence is simple and consists of dolomite-pyrite-galena-sphalerite-calcite. The mineralization is tectonically and unconformity controlled. Microthermometry of fluid inclusions in sphalerite indicates that ore precipitated from a NaCl-KCl-CaCl2-MgCl2 basin-derived hot (Th= 94 -170°C) and saline (Salinity = 13.8 -27.3 wt% NaCl eq.) mixed ore-forming fluid. Post-ore calcite also formed from a similar brine (Th = 176-206 °C, Salinity =17.6 -20.5 wt% NaCl eq.). The δ34S values for sulfides range from 7.8 to 23.4‰ V-CDT with most values in the range of 16 to 23.4‰ V-CDT. Sulfur was mainly derived from the Triassic-Jurassic sulfates through thermochemical-sulfate reduction. The carbon-oxygen isotope values of calcite are overall similar to that of the barren Bajocian limestone and dolostone indicating that the calcite-forming fluid is in equilibrium with the carbonate host rock. Galena samples have a homogeneous Pb composition with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios ranging from 18.358 to 18.376, 15.636 to 15.663 and 38.486 to 38.606 respectively. This Pb isotopic composition points to the Paleozoic siliciclastic rocks as the main source of lead and presumably other metals with a possible contribution of Precambrian rocks. The long-distance fluid flow through a thick sequence of Paleozoic-Jurassic rocks ensured the homogeneity of Pb isotopes of the ore-forming fluids before they reached the

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RESUMELa compilation des données géologiques et géophysiques (magnétique et gravimétrique) et l'élabora-tion des modèles tridimensionnels correspondants ont démontré l'enracinement des minéralisations qui a permis la remise en activité de la mine Draa Sfar après 23 ans d'arrêt. Les ressources géologiques ont été multipliées dix fois en trois années pour atteindre 10Mt à 5,39% Zn 1,94%Pb et 0,34%Cu. Cette méthodologie d'exploration basée sur les modèles géologique et géophysique tridimensionnels devient de plus en plus utilisée dans l'exploration minière stratégique et tactique en raison, entre autres, des avancées en informatique et de la disponibilité d'outils de modélisation spécialisés. Elle pourrait être d'un grand secours pour le développement minier de la province des amas sulfurés des Jebilet de Guemassa et par extension à d'autres gîtes présentant des caractéristiques géologiques et métallogéniques similaires. Mots ABSTRACTThe compilation of geological and geophysical (magnetic and gravity) data and the development of the corresponding three-dimensional models have allowed the recognition of the deep mineralized structures, and helped the reopening of the mining after 23 years of inactivity. Geological resources were increased tenfold in three years to reach 10Mt at 5.39% Zn, 1.94% Pb and 0.34% Cu.This exploration methodology based on three-dimensional geological and geophysical models becomes increasingly used in mining exploration strategy after the improvement in the computing capacities of the modelling tools. The results from this study could be helpful for the development of mining massive sulphide deposits in the Jebilet province of Guemassa and by extension to other deposits with similar geological and metallogenic characteristics.

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